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Time domain heart rate variability as a predictor of long-term prognosis after acute myocardial infarction
Ping-Yen Liu1, Wei-Chuan Tsai, Li-Jen Lin
1Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Insights
Reduced heart rate variability (HRV), specifically SDNNi below 30 ms, predicts cardiovascular death in myocardial infarction (MI) survivors. This finding offers crucial insights for long-term prognosis in post-MI patients.
Area of Science:
- Cardiology
- Medical Prognostics
- Heart Rate Variability Analysis
Background:
- Decreased heart rate variability (HRV) is a known predictor of mortality post-myocardial infarction (MI).
- The prognostic value of time-domain HRV parameters in MI survivors remains debated.
- This study investigates the significance of multiple time-domain HRV metrics for long-term outcomes.
Purpose of the Study:
- To evaluate the prognostic significance of five time-domain heart rate variability parameters.
- To assess their predictive value for cardiovascular and sudden cardiac death in patients surviving their first MI.
- To determine if specific HRV metrics offer superior long-term prognostic information.
Main Methods:
- 24-hour ECGs were analyzed in 260 first-time MI survivors post-discharge.
- Five time-domain HRV parameters were measured, including standard deviation of NN intervals and SDNNi.
- Patients were followed for a median of 67 months to track cardiovascular events.
Main Results:
- Cardiovascular death occurred in 21% of patients, with 15% experiencing sudden death.
- SDNNi < 30 ms was a significant predictor of cardiovascular death (HR, 4.98) and sudden cardiac death (HR, 5.02).
- Other significant predictors included ventricular premature complexes, advanced age, and reduced left ventricular ejection fraction.
Conclusions:
- SDNNi is a significant time-domain parameter for assessing long-term prognosis in patients post-MI.
- Low SDNNi (< 30 ms) identifies high-risk individuals for cardiovascular and sudden cardiac death.
- These findings support the routine use of SDNNi in the risk stratification of MI survivors.
Background And Purpose:
Decreased heart rate variability (HRV) has been shown to be a predictor of both sudden cardiac death and cardiovascular death among patients surviving acute myocardial infarction (MI). However, the prognostic significance of time domain HRV in patients with MI is still controversial. In addition to the mean of all normal-to-normal (NN) intervals, we analyzed the prognostic significance of the 5 most widely used time domain parameters of HRV during long-term follow-up in patients surviving their first MI.
Methods:
Five time domain measures of HRV from 24-hour ECG were obtained after discharge in 260 consecutive patients (207 males; mean age, 60 years) surviving their first MI. These parameters included: standard deviation of all NN intervals, mean of standard deviations of all NN intervals in all 5-minute segments (SDNNi), standard deviation of the average of all NN intervals in all 5-minute segments, the square root of the mean of the sum of the squares of differences between adjacent NN intervals, and percentage of differences between adjacent NN intervals > 50 ms.
Results:
The study endpoint was cardiovascular death. After follow-up for 67 months (range, 1 to 114 months), there were 55 cardiovascular deaths (21%) including 39 sudden deaths (15%). Multivariate Cox regression analysis showed that SDNNi < 30 ms was a significant predictor of cardiovascular death (hazard ratio, 4.98; 95% confidence interval [CI], 2.03 to 12.21; p < 0.001) as was number of ventricular premature complexes >/= 10 beats/hour (hazard ratio, 5.34; 95% CI, 2.26 to 12.62; p < 0.001), age >/= 70 years (hazard ratio, 3.65; 95% CI, 1.44 to 9.23; p = 0.006), and left ventricular ejection fraction < 45% (hazard ratio, 3.29; 95% CI, 1.13 to 9.57; p = 0.03). SDNNi < 30 ms was also an important predictor of sudden cardiac death (hazard ratio, 5.02; 95% CI, 1.49 to 16.85; p = 0.009).
Conclusions:
These data suggest that SDNNi is a significant time domain parameter of HRV for long-term prognosis in post-MI patients.
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